Solar Water Heating: In the Shadow of PV

It would be hard not to notice the rush of activity in the worldwide photovoltaic marketplace in recent years, but you may not have noticed that at the same time, solar thermal technology has been rapidly overshadowed by the unprecedented growth and popularity of PV. Once heralded as the most cost effective way to capture and store the sun’s energy, sales of solar water heating systems have not kept pace with the new generation of “plug and play” PV products. The reality of solar thermal’s technical complexities, in combination with misinformation about solar thermal’s versatility and practicality have lead to stagnation in the marketplace. In fact, the rise of cheap PV lead to Martin Holladay’s pronouncement that “Solar Thermal is Dead” in a 2012 article at greenbuildingadvisor.com.

“Solar water heating is only practical in southern climates…”

We often hear that solar water heating doesn’t make sense in northern states, like Minnesota and Wisconsin. In fact, Holladay makes the case that with plummeting PV prices, it may actually be cheaper to heat water with PV now than it is to us a solar thermal system. With PV panel prices dropping below $1/watt, this may be even more true than when Holladay’s article was initially published. Still, thanks to incentive programs, affordable solar domestic hot water (sdhw) systems are still going up in northern states. According to the Daily Northwestern, The city of Evanston Illinois has had 85 new DSHW systems installed this year. In addition, niche markets for solar water heating are popping up, in the hotel industry, greenhouses and residential and public pool heating.

The solar heated greenhouse at Dickinson college photo: dickinson.edu

Meanwhile, SDHW continues to see modest growth and continued popularity in southern states like Arizona and Florida. Can solar water heating make a comeback in the US? As with PV, the key will be seeing the installed price come down, and sadly, right now, that isn’t happening.